it's really easy.
1. Install the CTI OS Agent Desktop application on agent PC's (by default, it installs the silent monitoring components as well)
2. Install CTI OS Supervisor Desktop application for the supervisor(s).
3. If the Ethernet cards of the Agent PC's are listed here: http://www.cisco.com/application/pdf/en/us/guest/products/ps14//c1221/cdccont_0900aecd800e3149.pdf , there is no problem. If not listed there, then take a look at http://www.cisco.com/en/US/customer/products/sw/custcosw/ps1846/products_tech_note09186a008075025a.shtml (applies to CTI OS monitoring as well)
4. Make sure there is a sound card installed in the supervisor PC -> calls monitored are output onto the soundcard
5. Make sure you have enabled the 'Span to PC port' option on the agent phones in the CallManager (disabled by default).
Well, that should be it...